1. Field of the Invention
This invention relates to motion vector generation of the type typically used within motion compensated image interpolation systems.
2. Description of the Prior Art
Motion compensated image interpolation for purposes such as standards conversion is known, e.g. conversion from film to television or from one television format to another. An example of such a system is described in British Published Patent Application GB-A-2,231,749 (Sony Corporation).
An important step in motion compensated interpolation systems is the generation and analysis of correlation surfaces to identify motion vectors. More particularly, the correlation surfaces are analyzed to find the point of maximum correlation (this may correspond to a minimum in a correlation surface), assess the validity of this point by means of various tests and output an appropriate motion vector determined by the position of the correlation maximum in the correlation surface. In addition, growing, weighting and interpolation techniques may be used to refine the process and improve reliability.
In known systems, each correlation surface is separately analyzed one at a time in a correlation surface sequential fashion. The analysis is done in this way to ease the process of finding values of maximum correlation within a surface by requiring only one (best known result) to be stored at any one time. A problem with this approach is that the input image data upon which the system operates is provided in a raster scan format across the entire image. In order that the correlation surfaces can be analyzed in a correlation surface sequential fashion, it is necessary that the data for each correlation surface, which in fact originates from only a portion of the overall image, be presented together to the analysis system.
This places a requirement that the data stream passing through the device is reformatted (re-ordered/"twisted") from a raster scan order based upon the whole image to a series of raster scans through each correlation surface representing only a portion of the image. Such a reformatting requires a disadvantageously large block of memory to perform. Furthermore, the techniques such as growing and interpolation that are used to improve the reliability and accuracy of the correlation surface analysis are more difficult to perform upon such twisted data.